1. Field of the Invention
The present invention relates to a magnetic recording/playback apparatus, and more particularly to a magnetic recording/playback apparatus having a magnetic head assembly adapted to be replaced by users.
2. Description of the Related Art
In a magnetic recording/playback apparatus, e.g., VTR, a plurality of magnetic head assemblies are arranged at regular intervals along the circumference of a rotating drum. Each head assembly includes a plurality of magnetic heads, e.g., recording heads, playback heads, and an erase head, which are each projected for a predetermined distance from the outer peripheral surface of the rotating drum, in the radial direction thereof. A magnetic tape, being transported so as to be wound around the outer peripheral surface of the rotating drum, is pressed against the magnetic heads, so that magnetic recording information is recorded on or read from the tape.
The magnetic heads are usually exhausted in about 500 hours, and may possibly be damaged during use. It is to be desired, in such a case, that users should be able to remove the rotating drum itself from the VTR, and replace the head assemblies on the spot, instead of having them replaced in a manufacturer's service station.
It is necessary, however, to maintain predetermined intervals between a plurality of magnetic heads, a predetermined length of projection of each magnetic head from the outer peripheral surface of the rotating drum, and a predetermined direction of projection of each magnetic head. That is, it is necessary that magnetic heads can be accurately positioned. If one head assembly includes only one magnetic head, the magnetic recording/playback performance can hardly be lowered even though the magnetic head is not located in a predetermined position. However, if one head assembly includes a plurality of magnetic heads (e.g., four in number), as in the case of a modern high-density recording/playback apparatus, such as a high-grade VTR using a one-inch tape, the magnetic recording/playback performance is considerably lowered unless the magnetic head is properly positioned.
Accordingly, each head assembly is mounted on the rotating drum by means of a position adjusting apparatus constructed as follows. Two pressure-contact spheres attached to the head assembly are pressed against a reference surface on the rotating drum. Also, an adjust screw attached to the head assembly is pressed against the rotating drum. The length of projection of each magnetic head can be adjusted by rotating the adjust screw. In other words, the head assembly is supported on the rotating drum at three supporting points.
It is difficult, however, to position the magnetic heads accurately by means of the position adjusting apparatus. For example, a gap may be formed between one of the pressure-contact spheres and the reference surface, so that the magnetic heads sometimes may fail to be properly positioned when the head assemblies are mounted on the rotating drum.
Thus, the replacement of the head assemblies requires a relatively complicated adjustment work. Therefore, it is hardly possible for those users who are inexperienced in such adjustment to replace the head assemblies. In such a case, the head assemblies are replaced in the manufacturer's service station or by a serviceman skilled in adjusting the magnetic heads.